A phylocarcinoembryonic antigen has been demonstrated on all epithelial cell neoplasms in man and its corresponding antibodies occur in the sera of patients with such neoplasms. This antigen shares antigenic determinants with a bovine associated mucoprotein (BAMP) that is a normal constituent of the epithelial cell membrane of the cow and also occurs free in milk. BAMP and anti-BAMP are associated not only with cancer but with a variety of immunologic disorders, all presumably sharing a common thymus defect. This study proposes to establish clearly the relationship of BAMP and anti-BAMP with a variety of clinical parameters in cancer patients and those with other immunological disorders and to determine the potential value of the BAMP system in the diagnosis of cancer. We endeavor to make physicochemical and immunochemical comparisons of the human BAMP equivalent (HAMP) isolated from a variety of human tumors, embryonic tissue, and other tissue in which it occurs. Also, anti-BAMP (HAMP) will be isolated from the serum of patients to identify its specificity, immunoglobulin class and associated characteristics. Finally, the immunohistochemistry of the BAMP (HAMP) system will be studied at the light and electron microscopic levels.